1. Field of the Invention
This invention relates generally to fire hydrants, and more particularly to improvements in fire hydrants of the frostproof type.
2. Statement of the Prior Art
Fire hydrants of the type including a valve stem and a connected valve supported for reciprocating movement in a vertical barrel are, of course, well known. Typically, such hydrants include a bonnet secured to the barrel, the bonnet having an internally threaded aperture which receives the externally threaded upper end of the valve stem. Alternatively, the lower end of the valve stem may be threaded and received in an internally threaded nut seated in the shoe, below the valve. In such hydrants, the valve stem is reciprocated by rotating the valve stem relative to the bonnet. Generally, the valve stem is rotated by a wrench or the like which fits about a suitably shaped projection at the top of the valve stem which protrudes through the bonnet. Fire hydrants fitting this general description may be found in sales brochures distributed by Waterous, South Saint Paul, Minnesota; Kennedy Valve Manufacturing Co., Inc., Elmira, New York; United States Pipe and Foundry Company, Smith Valve and Hydrant Division, East Orange, N.J.; and Clow Corporation, Eddy-Iowa Division, Oskaloosa, Iowa.
The desirability of seating the valve above its seat so that the water pressure in the shoe biases the valve to the open position to reduce opening time has also be recognized. Such arrangements also reduce water hammer upon closing since the valve cannot jump to its seat but rather closes gradually against the water pressure. Hydrants operating according to this principle are also disclosed in the above-mentioned literature, particularly the Clow brochure. See also U.S. Pat. No. 2,580,197.
Still others have recognized that the accumulation of water and subsequent freezing thereof between the mating threads of the valve stem and the bonnet or nut which holds it in place can block reciprocating movement of the stem to open the valve, as can corrosion of the threaded components. Based on this, fire hydrants using means other than mating threaded members to accomplish reciprocating movement of the valve stem and connected valve have been suggested. See, for example, U.S. Pat. No. 202,316 wherein a lever secured to the stem and projected through the side of the barrel is used to reciprocate the stem and the connected valve. See also U.S. Pat. Nos. 3,532,108 and 3,532,109, wherein the valve stem is reciprocated by a detachable mechanism securable to the bonnet for engagement with the top of the valve stem protruding therethrough. In each of these patents, however, the hydrant disclosed is of the type wherein the valve is biased to the closed position by the water pressure in the shoe.
Where non-threaded arrangements are used with hydrants wherein the water pressure biases the valve to the open position, means must be provided for securing the valve in the closed position until opening is desired. In U.S. Pat. No. 2,580,197, this is accomplished by a coil spring disposed about the upper portion of the valve stem and having one end seated on the bonnet and the other end seated on a flange secured to the stem. Thus, the force exerted by the spring on the flange biases the valve stem to the closed position against the water pressure in the shoe. A handle extending through the top of the bonnet is provided for moving the valve stem against the bias of the spring for opening the valve. In arrangements of this type, it is apparent that the coil spring is continuously in opposition to the water pressure acting on the valve. Thus, after a period of time, the spring may lose its elasticity and even break.